Definitely sounds like a diesel bug or waxing of the FAME in the fuel. On the recommendation of the Bavaria Agent in Malta, Anthony Camilleri and the Volvo agent, I have installed an in-line fuel strainer (not filter) to catch lumps of gunk before it reaches the fuel off/on switch. Cost 4 euros.
The off/on switch aperture is much smaller than the fuel line and any gunk will block here. The strainer catches the large lumps likely to block the switch but allows small gunk through to collect in the fuel filter. The fuel strainer is almost impossible to block and you can easily see how blocked it is through the clear plastic cover.
You are likely to have a thin film of gunk coating the inside of your fuel tank. This is what breaks off in rolly sea conditions. This gunk is hard to see, even if you have an inspection cover for your fuel tank. The Maltese approach is to not worry about cleaning tanks or using treatments for diesel bug but to recognise that "Bug" is just a part of life and merely needs to be caught in the strainer. Strainers need to be changed when you see the build up.
After a diesel bug issue early this year I installed a strainer as above. I also use Startron and noted that the "Bug" caught in the strainer dissolved after a long trip under motor. For this reason, I continue to use Startron.
Craig
s/v "Shirley Valentine"
